To paraphrase Clint Eastwood’s Dirty Harry, opinions are like backsides. Everyone has one. Of course, the loose-cannon cop used a less family-friendly anatomical term to refer to one’s posterior. But his observation has never been more pertinent, thanks to our obsessive need to instantly express our reactions to every pop-cultural blip on social media.

That is especially true when it comes to passing judgment on films. The minute that a hotly anticipated summer blockbuster opens – or, even more common, its first trailer hits the internet – Twitter is awash in 140 characters-or-fewer reviews insisting that a new release is a masterpiece, a bomb or somewhere in-between.

The dissonance that results from such a tweet-nami of reactions can overwhelm. Of course, any fool could state that they love or hate a film. I should know. I’ve been a professional movie reviewer off and on for years. The hard part is pinpointing exactly why a film is a must-see or a should-miss with a perceptive analysis that goes beyond mere plot summarizing.

To the rescue of those who would like to have a more informed way to judge potential classics or turkeys is Ann Hornaday, the esteemed chief film critic for the Washington Post. Her "Talking Pictures: How to Watch Movies" is like enrolling in a master class on the art of cinematic parsing – and is a lot cheaper than signing up for a college course. It is also more fun since Hornaday wisely employs quotes and anecdotes from a wide range of major talents both in front of and behind the camera, many taken from interviews she has done over the years.

In her intro, she tells of a fellow journalist who once told her to ask three questions before writing any review. Namely, what was the artist trying to achieve? Did he or she achieve it? Was it worth doing? Hornaday then breaks down the process of answering those queries into seven chapters: The screenplay, acting, production design (which includes sets, costumes and makeup), cinematography, editing, sound and music, and directing. Basically, these are the key ingredients that, in concert with one another, can make or break a film production.

The author also shows her smarts by designating George Clooney as her first namedrop, recalling how he revealed that his experience on the much-derided "Batman & Robin" (yes, the one with the rubber-nippled Bat suit) taught him the importance of a solid script. As a result of this revelation, his next three features – "Out of Sight," "Three Kings" and "O Brother, Where Art Thou?" – went a long way to right his career track. The moral of the story, according to Clooney? “You can make a bad film out of a good screenplay. I’ve seen that happen a lot. But you can’t do it the other way around.”

As is a critic’s prerogative, Hornaday plays favorites when choosing films to illustrate her points. The “un-sleek” works by writer-director Kenneth Lonergan ("You Can Count on Me," "Margaret" and "Manchester by the Sea," an Oscar winner for original screenplay) are heaped with praise in several chapters, including screenplay, acting and editing. Hornaday allows Lonergan to diss one of the most enduring of romantic movie clichés. “The first time the couple meets, first they are really snarky with each other, and competitive, and they put each other down, and ten minutes later, they are in love,” he says. “But most girls I ended up with I got along pretty well from the beginning. The tensions came from other things. And those tensions are there for anyone who wants to pay attention to them.”

And if books could have a drinking game, one may get a buzz while taking a sip every time Hornaday mentions "All the President’s Men," the 1976 political thriller about the journalistic takedown of President Richard Nixon by intrepid Washington Post reporters Carl Bernstein and Bob Woodward as played by Dustin Hoffman and Robert Redford. Yes, such frequent mentions are a bit incestuous. But the film is not only timely given the current president’s travails with the media, but is a textbook example of how to sublimate star power for the sake of building tension and veracity.

“My whole focus was being totally accurate, trying to downplay whatever personality I had to fit Woodward,” Redford told Hornaday decades after the film came out. While he and Hoffman might have attracted ticket buyers, it was the taut and fraught fact-finding process that kept the audience riveted. In fact, director Alan J. Pakula was such a stickler for authenticity that his production designer not only reproduced the Post’s newsroom to scale, he flew in actual garbage from real reporters’ trash cans to use on the set.

She also extols the way Pakula used an overhead camera that pulls away from the reporters as they meticulously go through countless book slips at the Library of Congress, causing them to shrink ever smaller onscreen while emphasizing the needle-in-a-haystack enormity of their task. As Pakula once said, “A story is told as much by what you don’t see, what you don’t show. If you show everything, nothing has importance.”

The book regularly lauds such stellar examples of moviemakers at the top of their game as "Goodfellas" (Martin Scorsese’s famous long, meandering Copacabana tracking shot), "Do the Right Thing" (Spike Lee’s use of a double dolly that makes it seem as if his actors are floating), "Children of Men" (Alfonso Cuaron’s emphasis on backgrounds as much as character) and "The Hurt Locker" (Kathryn Bigelow’s choice to kill off her cast’s best known actor, Guy Pierce, in the opening scene). But Hornaday is at her opinionated best as she throws stones at the makers of such best-picture Oscar winners as Titanic (she decries James Cameron’s lack of subtlety when portraying characters, labeling them “human billboards for Good and Evil”), "The King’s Speech" (she slams Tom Hooper’s frequent use of static distempered walls as backdrops, declaring, “Background or foreground, a movie’s design should be alive as the people within it”) and "The Revenant" (Alejandro Gonzalez Inarritu’s over-insistence on softening and humanizing Leonardo DiCaprio as trapper Hugh Glass).

Along the way, you will likely pick up enough movie-related lingo such as “second-act slump,”“plotty,” “cutty,” “whammies,” “magic hour” and “Dutch angles” to impress whoever you are arguing with on Facebook about which entry in Ridley Scott’s "Alien" franchise is the best.

But here is why I know Hornaday has provided a valuable service: Anyone with a reasonable knowledge of the history of film could probably write a serviceable chapter on actors and their craft. But to be able to explain aspect ratios (yes, it involves math) when it comes to cinematography in a cogent and entertaining way with vivid examples is an art in itself.

Susan Wloszczyna is a former film writer for USA Today and a current contributing critic to the Roger Ebert website.